Revision of Bryosoan Genera.—Cumings. 211 
encircled by a conspicuous definite dark ring separated from 
the zocecial cavity by a light band, usually narrow, of light- 
colored schlerenchyma. Between the dark rings of adjacent 
zocecia is a belt of light-colored material in which the acantho- 
pores are lodged. The mesopores may have definite dark 
rings surrounding thent, or indefinite walls, in which case they 
appear merely as clear patches in the median light-colored 
zone. This peculiar wall structure variously modified by the 
thickening or thinning of the walls, or development of namer- 
‘ous mesopores holds throughout the genus Dekayia (as emend- 
ed) and serves as its most invariable character. 
Figure 13, Pl. [X, is a tangential section of a specimen ex- 
ternally similar in every respect to the one from which the sec- 
tions just described were cut. The section differs from the 
preceding in the more numerous mesopores and acanthopores 
and in the presence of an occasional acanthopore of large size. 
The latter feature is better shown in another portion of the 
same section (fig 12, Pl. IX), and in still another portion, 
which cuts the submature region (fig. 9, Pl. IX). In the latter 
the difference in size is pronounced as is still better shown in a 
further magnification of the same section (fig. 6, Pl. X). In 
longitudinal sections the large acanthopores can sometimes be 
traced into the axial region. The small ones are present only 
in the mature region. 
I am not sure that I have detected a pellicle over the sur- 
face of any specimen of Dekayia perfrondosa. One specimen 
seems to show it. Such a character must, at all events, be of 
small importance and may very well be due to accidental 
causes. It is seen in Dekayella Ulr., as well as in Dekayia Ulr. 
Dekayia subpulchella is very closely related to D. perfrondo- 
sa, probably a good variety of the latter. In this form the walls 
are thick (fig. 14, pl. IX; fig. 4, pl. X) and the acanthopores 
conspicuously of two sizes. Not all specimens of D. subpul- 
chella show the latter character, though my sections have re- 
vealed it in most cases. 
From the above discussion it appears that the three genera 
of Ulrich*, Dekayia, Dekayella and Heterotrypa constitute but 
*In justice to this pre-eminent student of Bryozoa it should be 
added that he has seriously considered combining the three, owing to an ‘‘al- 
most complete chain’’ of connecting forms. (Geol. Minn. iii, 1893, pp. 269, 
270.) LIbeheve that with the evidence herein presented, before him, he will no 
longer hesitate to do so. 
